[gentoo-dev] Re: How to support C++11 in libraries?

[Martin Vaeth <vaeth@mathematik.uni-wuerzburg.de>]

Jan Kundrát <jkt@gentoo.org> wrote:
>
> Before you invest any more time in this, please understand that C++98 and
> C++11 are source-incompatible.

The question is what impact this theoretical incompatibility in a few
corner cases has in practice.

> There is no way to expect that a package builds fine when you
> throw -std=c++11 on it.

Yes, but the same is true for any gcc upgrade.
I repeat that numbers are necessary: If practice shows that there is only
a few packages in the tree needing a few trivial patches then the same can
be assumed about 3rd party software. The situation is rather different if
it turns out that almost nothing runs without severe patches.
Nobody can know the answer without actually trying.
However, I would be very surprised if the latter is true:
The example with string reference-counters which you gave is IMHO typical;
one would really need to write strange code to make it work *with* reference
counters but break without. Hard to believe that this happens in practice.
What *will* happen in practice is that the execution speed changes (probably
getting slower, but there might also be exceptions).